This section provides background information related to the present disclosure which is not necessarily prior art.
Temperature measuring devices are widely used in various fields, such as a clinical thermometer for measuring body temperature, a temperature measuring device in a temperature controller, etc. In order to achieve better performance of temperature controlling when using a temperature controller, the temperature measuring device therein should have a high temperature resolution in a wide measurement range.
In the past, in order to achieve a high temperature resolution, A/D converters were not used to measure temperature. This is because a temperature measuring device utilizing an A/D converter was too costly and was unable to keep the high temperature resolution in a wide measurement range. But with the development of hardware technologies, the cost of a temperature measuring device utilizing an A/D converter has been decreased to a more affordable level. In some special applications, such as in a temperature controller, a temperature measuring device utilizing A/D converter has become the preferred choice for temperature measurement because of the short time of the measurement and other advantages associated with utilization of an A/D converter.
Presently, however, a temperature measuring device utilizing an A/D converter provides only one reference voltage for the A/D converter therein. But the reference voltage for a certain A/D converter generally corresponds to the measurement range of the temperature measuring device. In order to achieve a wide measurement range, it is common to choose a large reference voltage for the A/D converter. But the larger the reference voltage is, the lower the temperature resolution is for the temperature measuring device. And, in case of utilizing one reference voltage, the resolution of the A/D converter is invariable. As a result, the resolution of the temperature measuring device decreases as the temperature increases, and it becomes unable to meet the requirement of certain temperature controllers. In addition to recognizing the above, the inventors hereof have further recognized a need for a temperature measuring device utilizing an A/D converter, which has a high temperature resolution in a wide measurement range.